In order to satisfy growing demand for bandwidth, control costs and still remain competitive, service providers are rapidly deploying the next generation of optical transport networks. As such, network manufacturers must ensure that the optical switches manufactured for use in optical transport networks are fully compliant with the ITU-T G.709 standard. The ITU-T G.709 standard defines the network interface for the transport of voice and data over the high-speed optical transport networks, which is defined in the ITU-T G.872 standard.
In many telecommunications systems, including optical transport networks as specified by ITU-T G.709, overhead information is used to transport system administrative information, such as configuration, management, address, timing, alarm indication and data integrity information, as well as other information. In many networks, including optical transport networks, this overhead information is transported as a portion of a data transmission frame.
In general, due to time division multiplexing techniques, many hierarchical layers of data, each having associated overhead data, can be present in a single high-rate data signal. Unfortunately, each of the hierarchical layers, and therefore their associated overhead, may have timing that is based on different clock frequencies, resulting in completely uncorrelated frequencies within a single data stream. This plesiochronous nature of the multiplexed hierarchical layers makes it extremely difficult to extract and insert overhead in a manner that is not costly.
Since the data streams that are multiplexed for transport across the optical transport networks as defined in the ITU-T G.709 standard may have different clock frequencies, overhead insertion and extraction must be supported for plesiochronous data streams. Since existing overhead extraction and insertion methods are based on processing of synchronous data streams, however, a new method of extracting and inserting the overhead data of plesiochronous data streams is required.